This invention relates to the use of sulfide-type copper ores, whether or not they have been beneficiated and concentrated, as electrochemically active ingredients in primary (non-rechargeable) and secondary (rechargeable) batteries employing aqueous or non-aqueous electrolytes, the latter including high temperature molten salt batteries.
In the search for substantially lower cost materials for the construction of electrochemical batteries, both primary and secondary, it has been discovered that copper ores containing either copper-sulfur compounds or copper iron-sulfur compound, with or without the presence of other metal sulfides or oxides, can be used as cathode active materials for both primary and secondary batteries using a variety of electrolyte systems. The removal of silica and silicates is desirable simply to reduce the bulk of the material to improve its electrical conductivity in the cathode mix. For this reason it is desirable, although not absolutely necessary, to employ ore concentrates from which silica and silicates have been removed by flotation and other processes. These concentrates still contain significant amounts of iron, silica and alumina.
Typical copper concentrate may contain 27% by weight of copper, 26% copper metal, 22% iron metal, 24.5% sulfur, 2.6% alumina, 0.3% calcia, 12.3% silica and 17.4% insolubles. The metal ore present simple or complex sulfides. A typical compound makeup of these concentrates can be 75% chalcopyrite (CuFeS.sub.2), 15% iron pyrite (FeS.sub.2), 1-2% bornite, 1% molybdenite and the usual silica, etc. In the copper refining process this material is fed into a smelter which upgrades the contents of copper and a "matte" is produced as an intermediate with a typical composition of 45% copper 24% iron and 25% sulfur.
Copper, iron, and sulfur form a large variety of compounds with various stoichiometric ratios. Extensive phase diagrams in this system have been described by R. A. Yund and G. Kullerud (J. Petrology 1966 Vol. 7 pp. 454-88). Typical compounds occurring in naturally found ores of the three elements are chalcopyrite (CuFeS.sub.2), bornite (Cu.sub.5 FeS.sub.4), and cubanite (CuFe.sub.2 S.sub.3), and idaite (Cu.sub.5 FeS.sub.6). These formulas are of course normal compositional expressions. In reality there is a compositional range for elements within a given compound structure particularly for the sulfur. Very often in nature, chalcopyrite is found with compositions CuFe.sub.2 S.sub.x where x may vary from 1.6 to 2.0.